1. Field of the Invention
The present invention relates to a gas combustion apparatus, and can be applied to a boiler.
2. Disclosure of the Prior Art
A gas combustion apparatus such as a boiler is disposed outdoors in some cases, and when rainwater enters an outer case thereof, there is a fear that a malfunction occurs in a combustion portion or an electrical component apparatus. Therefore, the gas combustion apparatus generally has a waterproof structure for preventing rainwater from entering the outer case.
FIG. 6 is a schematic vertical sectional view of a conventional boiler 1 as the gas combustion apparatus.
The boiler 1 includes a boiler main body 1A. An air supply fan 12 disposed in a lower portion of an outer case 10, a combustion unit 11 incorporating a gas burner therein, a heat exchange unit 13, an exhaust collector 14 and an exhaust cylinder 15 are connected to one another in this order in an upper portion of the boiler main body 1A.
The outer case 10 includes a case main body 2 accommodating the boiler main body 1A therein, and a front cover 3 for covering an opening formed in a front surface of the case main body 2. An exhaust cylinder insertion opening 300 is formed in the front cover 3, and the exhaust cylinder 15 of the boiler main body 1A projects outside from the exhaust cylinder insertion opening 300.
The front cover 3 has an outer peripheral flange 3a projecting toward a rear end peripheral edge. The outer peripheral flange 3a is superposed on an outer peripheral flange 2a projecting toward a front end peripheral edge of the case main body 2 and is fixed thereto by means of a screw.
Therefore, even when the boiler 1 disposed outdoors is exposed to rain, rainwater which fell on the upper surface of the case main body 2 or the front cover 3 is held back by the outer peripheral flanges 2a and 3a and does not enter the outer case 10, and adverse influence on the inside boiler main body 1A and electrical component apparatus 16 is avoided.
According to the conventional technique shown in FIG. 6, however, outward appearance of the boiler 1 is deteriorated due to the overhanging outer peripheral flanges 2a and 3a from the case main body 2 and the front cover 3, a dust cloth used at a time of cleaning is caught in the outer peripheral flanges 2a and 3a and this hinders cleaning operation.
FIG. 7 shows another conventional technique capable of solving this problem.
According to this technique, an inner peripheral flange 20 formed on a peripheral edge of a front end opening of the case main body 2 and an inner peripheral flange 39 formed on the rear end peripheral edge of the front cover 3 are fixed to each other by means of a screw (not shown) through a packing material 17. According to this technique, the packing material 17 prevents rainwater from entering from a connected portion between the case main body 2 and the front cover 3, and there are no members corresponding to the outer peripheral flanges 2a and 3a hanging over the outer peripheries of the fitted portion between the front cover 3 and the case main body 2 unlike the conventional technique shown in FIG. 6 and thus, the outward appearance of the boiler 1 is not deteriorated and the cleaning operation can smoothly be carried out.
According to the boiler shown in FIG. 7, however, the packing material 17 is simply sandwiched between the inner peripheral flange 20 and opposite inner peripheral flange 39 of the case main body 2 and the front cover 3, respectively, and the outer periphery of the packing material 17 is exposed to outside. Therefore, the packing material 17 is exposed to the natural environment such as sunlight and rainwater. Thus, there is a problem that the packing material 17 is deteriorated with time and the waterproof is prone to be deteriorated.
According to the conventional boilers, the two requirements, i.e., a requirement of outward appearance and cleaning easiness of the connected portion between the case main body 2 and the front cover 3, and a requirement of the waterproof lasting for a long term can not be satisfied at the same time.